Antibiotic resistant bacterial infections caused by both Gram-positive and Gram-negative pathogens pose a serious threat to human health. Resistance is increasing while research into new antibiotics and possible new targets is lagging. Both Gram-positive and Gram-negative bacteria are surrounded by a cross-linked carbohydrate polymer, peptidoglycan, which is conserved in all bacteria. This polymer is essential for bacterial survival because it stabilizes the cell membrane against high internal osmotic pressures. Peptidoglycan biosynthesis is a major target for antibiotics because interfering with this process leads to cell lysis. This research is directed towards understanding the mechanisms of action of vancomycin, penicillin, and moenomycin, important antibiotics that represent three classes of antibiotics that inhibit peptidoglycan synthesis. To understand the biological mechanisms of these drugs, an integrated program involving synthetic organic chemistry, biochemical and microbiological assays, structural studies, and bacterial genetics will be employed. A better understanding of how these drugs kill might lead to therapeutic strategies to improve their spectrum of activity and make them more effective at killing resistant microorganisms. Since these compounds target a fundamental metabolic process in bacteria, a better understanding of this process could lead to new antibiotic targets or strategies as well. PUBLIC HEALTH RELEVANCE: Resistance to common antibiotics poses a serious threat to public health. The research proposed here is directed towards understanding the mechanism of action of three classes of antibiotics that inhibit bacterial cell wall synthesis. A better understanding of how these drugs kill might lead to therapeutic strategies to improve their spectrum of activity and make them more effective at killing resistant microorganisms.